The present invention relates to a motor-vehicle door latch. More particularly this invention concerns such a latch which has a remotely controlled motor that can open it.
A motor-vehicle door latch of the type used on a trunk lid has a housing normally mounted on the door and carrying a pivotal fork that can engage in a latched position around a door bolt carried on a door edge or door post and that can, in an unlatched position, allow the door bolt to move out of the latch. Of course the fork could be carried on the vehicle body and the bolt on the door to the same effect. A pawl is pivotal on the latch housing between a position engaging the fork and holding it in the latched position and a freeing position allowing the fork to move into the unlatched position. Respective fork and pawl springs normally urge the fork into the unlatched position and the pawl into the holding position.
As described in U.S. Pat. No. 5,020,838 of Fukumoto such a latch can have a small electric motor with a rotary output carrying a worm meshing with external teeth on an operating wheel in turn carrying a pusher element engageable with the pawl to move it into its freeing position. A separate mechanical linkage connects the pawl to a lever in the vehicle so that, if the motor fails, for instance when the electric power is lost, the latch can be operated manually.
This arrangement is fairly bulky and complex. In particular its overall depth is considerable so that it cannot readily be incorporated in a trunk lid which offers much less room than a vehicle passenger door. The complex and bulky structure is also somewhat expensive to manufacture, adding to the cost of the latch.
It is therefore an object of the present invention to provide an improved power-open motor-vehicle door latch.
Another object is the provision of such an improved power-open motor-vehicle door latch which overcomes the above-given disadvantages, that is which is of simple and compact construction, yet which allows for remote power actuation and remote manual actuation of the latch.
A motor-vehicle door latch has a housing, a fork pivotal on the housing between a bolt-retaining latched position and a bolt-releasing unlatched position, and a pawl pivotal on the housing between a holding position engaging the fork and retaining it in the latched position and a freeing position allowing the fork to move into the unlatched position. According to the invention a wheel rotatable about an axis has a radially directed cam surface on which rides a projection on the pawl. A drive motor can rotate the wheel and thereby engage the surface with the projection to displace the pawl into its freeing position. A spring is braced between the pawl and the housing and urges the pawl into the holding position and the projection into engagement with the surface. Furthermore the wheel has a groove having a pair of ends, one radially directed flank formed by the cam surface and an opposite radially directed flank forming another surface. The cam surface is formed as a spiral generally centered on the wheel axis and the other surface is generally centered on the wheel axis. The groove has a wide end and a narrow end.
The use of a cam rather than a pusher element allows the system to be made very compact, and allows a small-torque motor to bring to bear the considerable force necessary to trip the pawl into its freeing position. In fact the structure can easily be designed using a transverse drive motor operating the wheel by means of a worm gear so as to be quite small.
The cam surface according to the invention is inward of the other surface so that the projection is cammed radially outward on movement from the holding to the freeing position by the wheel. In addition a manual-actuation lever is coupled to the pawl for pivoting same from the holding to the freeing position when the projection is at the wide groove end. The pawl has a pivot and the lever is coaxially pivoted with the pawl and has an end coupled to the pawl at the projection. Thus the latch can be opened manually in case the motor or its power supply fails.
The projection according to the invention has a dimension measured radially of the wheel which is slightly smaller than a radial dimension of the groove at the narrow end. Normally it is formed as a cylindrical pin that extends parallel to the wheel axis.
In accordance with the invention a spring urges the wheel into a position with the projection engaging in the wide groove end. It does so with enough force to overcome the drive, so long as it is not energized, so that the spring will return the latch to a position in which it can be manually opened if power fails at any time. This spring is a spiral spring connected between the housing and a shaft of the wheel.
The wheel shaft has a slotted end so that a tool can be fitted to the slotted end to manually rotate the wheel. In addition a rubber bumper is provided on the housing engaging the fork in the unlatched position.